The present invention relates to a novel organsilicon compound never described in any of previous literatures or published documents or, in particular, to a class of novel organosilane compounds with an epoxy group bonded to the silicon atom in the form of a 3,4-epoxycyclohexyl group and at least one alkenyloxy group directly bonded to the silicon atom in a molecule. These compounds are useful as a coupling agent or an adhesion-improving agent owing to the high reactivity thereof.